Grease composition



Dec. 2l, 1948. R. L, MERKER 2,456,642

GREASE COMPOSITION Filed Aug. 13, 1946.

2O 30 40 70 8O 90 I TEMPERATURE IN DEGREES FAHRENHEIT VISCOSITY CHARTFOR BLENDED LUBRIGANTS OO O O O O OO O O O O O 0 n Om Y* 'D 'n Q' OQ OOOO OID OQ@ qt0 N SBXOLSLLNBO NI ALISOOSIA SILVWSNDI Zlvwemm ROBERT LLMERKER @muy ' .blended silicone-diester .duidsas bases.

.commonly used additives ,readily soluble in the n'uid. v

'GnEAsncomosrrIoN l l maremma-keanu@ siterz'avi'yi; .a innemenlitmus,issefserimmeeoies n'fciaims. (el/aszi--Aa-.nff

\ .(Granrea 'under theses 6r Maren' amended April-so', me; 3ro oc. 757)Y My invention relatesto lgrea'se'ompositio'ns' and particularly'togrease compositions ut The resistance -of silicones' to.oxidati`on"andignition would seein to make their `employment in 4the art, ofNmanufacturing grease decidedly ad' r vantageous over theus'epof theconventionalg' purely 'hy'clrocarbg'in'I iiuidbases'. l, However, their4uses in this field have heretofore been necessarily limited' by theirvery natur-ein resistingthe incorporation ofv `important additives.A-S-uch ad' l ditixes include oxidation, corrosion', and rustVinhibitors, polymers, and thickeners such as 1 of siliconesanddistrsform the subject'matter metallic soaps. AThe incompatibility ofsilicone -iiuids and the soaps'necessa'ryto thicken them to a greaseconsistency tends to cause excessive ibleeding or separationwheri'silicne -greases are used, and the'methods for successfullyblending these components; because of thehinherent` in- .compatibilityof silicones and soaps; are 'necesi sarilyintricateandexpensive.' The'tendency of' silicones to seize, rather thanY ifo lubricate'certainmetal .on metal surfaces, has been another severe limitation in theirapplicability to high speed and high temperature operation. Thus, thestriking properties of this-family of compounds have not been utilizedin grease compositions to the fullest extent. f f

It is a fundamental object of my invention to obviate some of 'thesedifficulties and extend the usefulness of silicones in theaart of greasemanu-.- facture.. 4'

It is another object of my invention to provide comprising a'blend ofmajor portions of a silicone and a diesterfrenders the'thickeners andother It is another objectof my invention to provide ha greasecomposition which is characterized by 'thejsilicone-diester b1endas abase .and a very highF4 -viscosity stability over a wide range oftemperatures.

3;. asse, as? a will be exemplified Tin the -detailed description,

. hereinaiterset forth.' -The scope ofthe inventing will beindicated bythe claims;

I havei discovered" that* by combining silicones andliquid diestersofdicarboxylic and hydroxy acids; the resultingv fluid blends possesssubstantially' all of the desirable properties of the silicone iiuidsand3 the diester fluids while th'e undesirable qualities oi thesilicones are substantially'eliminated. 'These duid-lubricantscomprising blends of my .copending 'applicatiom Serial -Numb'en 690,194,led of even date herewith. l a

`Using such blended base uds I have disi covered further that highlystable grease's may be simply andQeconomically,produced and consistentlyreproduced. The'grease .compositions of y. l-my invention display goodoxidation resistance@ good lubricating quality, easycompatibilitywithsoap thickeners1a`nd-\\v`arious oxidation and rust inhibiting additives.l l

According to my invention. any liquid diesters, .preferablylthose whichhave boiling points about .150 C., may be'used'in ,combination with thea grease composition fin which the base fluid,

desired silicone to. prepare the baseI 'uii.'-A

40may be any of those which are soluble in the ruis a further `objectbrmy invention to provide a silicone-disaster greasev composition.whichI is extremely resistantto oxidation.

h It is a further objectof lmy'invention 'to provide a silicone-diestergrease compositionl suitable for' l use in delicate instruments. inhigh-speed, highwhere R1, Rs, R4 and Rs can be alike or temperatureoperations,l and in general purpose lubrication.

Another object .of

IOther objects and ,advantages of my invention will in part b eobvious'and in part appear here@ inafter. l Q "p My invention,accordingly comprises' metal soap. greasesf utilizing -silicone-#diesterblends asv base fiuids, said greases possessing the characteristics.'

prperties, and the relation of components which my. invention is provide.l a method for producing silicone greases: j

desired diester liquid. Among these fare. alkyl, aryl, alkaryl, aralkylstraight and branched chain lsilicone polymers, such as dimethyl,diethyl, ethylv,

methyl, diphenyl, ditolyl, vphenyl-tolyl,v phenylmethyl, ethyl-phenylsilicones and others whichy conform to the general structure diierentand may be any .of the above mentioned 1 radicals, andn may be any wholenumber greater vthat l. Cross-linked silicone polymersA may be.

.55 used equally well provided they are compatiblel with the chosendiester fluid over the temperature range in which the composition istobe' used.' Silicone uids .available commercially; arefgenerallyassigned a formula. like that sketched, ibut '69 it is; understood inthe that a given uid may the viscosity stabilityof the fluid.

3 contain chain compounds having the Si-O linkage and many cross-linkedand divided elements.

Metallicsalts of fatty acids having from to carbon atoms in thealiphatic chain are used as the metal soap thickeners in my invention.Metals such as aluminum, lead, zinc, and maginesium, alkali metals suchaslithium,` sodium, and potassium, and alkaline earth metals such ascalcium, barium, andstrontium are, most frequently used, although metalssuch as copper', manganese, mercury, bismuth, chromium, iron,` cobalt,nickel may be used.

I `In addition to the soap thickeners added,- various l balancingingredients such asoxidation, rust. and corrosion inhibitors, polymerthickeners, extreme pressure additives, and the -like as exempliied by:

Polymer thickeners:

Polymethyl methacrylate Polybut'ene f Anti-oxidants:

4-tertiary-2-phenyl phenol Diphenyl amine l `f Rust inhibitors: i

Zinc naphthenate Barium mahogany sulionate ASorbitan monooleateAnti-wear additives:

Tricresylphosphate may be incorporated with the base iuid, as conditionsof operations dictate, Total balancing ingredients will be less than 3per' cent by weight of the composition.

The base fluid lubricant of my invention comprises 'essentially a blendof between about 5 and 95 per centlby weight of Ysilicone polymerandbetweeny about 5 and 95 per cent by weight of liquid diester. f v

In order t`o illustrate that" the combination of a' silicone polymer anda diester uid in the proporfy tions defined preservesl the desirableproperties of the silicone. masks undesirable ones, and in- CTI ,corporates desirable properties of the ester, a

series of base fluid 'lubricants were prepared and tested.' Typical testdata-are shown in Table I and illustrated by curves in the appendedligure.

Specific fluid blends were prepared from varying proportions ofpolymethylphenylsiloxane, (aromatic-aliphatic ration-5.51) anddi-2-ethylhexyl adipate.y When an oxidation inhibitor was used,ll-tertiary butyl-Z-phenyl phenol was r chosen. The polymer thickenerwhen used was a polymethyl methacrylate.` i

The particular components of any one mixture were heated together withstirring to about 350 F. to 400 F. to insure the attainmentof complete55 solution.

TAaLE I Kinematic viscosities in I l ASTM Reference Centistokes SlopeViscosity to Figure 0:- y index fo F. F. 210er. 21 F curve 1... 107 s.22 l 2. as 0.765 121 65 Curve 2- e 2628v 96. 86 21. 96 0. 484 155 Curve3. 550. 1- 22. 57 5. 425 0. 665 170 Clirve'4 f 827. 3 29. 30 6; 716 0.635 165 y Curve 5. 1386 39. 70 B.l 706 v 0. 603 160 CulYe 6.-. 261059.27 I12.29 0.587 l55 Referring to the figure, curves are plotted, ac-l70 cording to the ASTM requirements., of the kinematic viscosities incentistokes as ,a function of temperature. The slopes of 'thesecurvesindicate Curve I represents vthe characteristics of the 75 purediester-and is givenas a basis for'comparison with the other curves;

` lubricant consisting of 69.8 partssilicone, 30 parts diester, and 0.2part oxidation inhibitor; c v V'Curve-4 represents the characteristics[of a fluid lubricant consisting of 79.8 parts silicone, 20 partsdiester, and 0.2 part oxidation inhibitor;

Curve 5 represents the characteristics of a fluidlubricant consisting of89.8 parts silicone, 10 parts diester, and 0.2 part oxidation inhibitor;p A

Curve 6 represents 'the characteristics of the pure liquid silicone -andis,g`iven as a basis forI l comparison with the other curves.

lIt will be noted that curves 34, and 5 possess substantially the sameslope as curve 6, indicating y that the desirable viscosityproperties ofthe silicone are maintained in the blended siliconediester liquids.Curve 2 shows-an improvement in the viscosity characteristics of theprepared lubricant over the pure silicone of curve 6. It is seen thatthe viscosity slopes of the prepared lubricants are real improvementsover the vis f cosity of the pure diester in curve I.

To illustrate'the degree -of compatibility of the base uid blends withthe various additives, all of the compound fluid lubricantsof'silicone-diester composition were storedat minus 40 F. for 10 'dayswith no separation of phases resulting therefrom. Although theproperties of a specificv silicone-diester combination were summarizedin the figure, it is to be understood that the invention is not limitedto the'speciflc example, 4but thatthe exampleis'merely an illustrationof one of its,` preferred embodiments.

The grease compositions of my invention consist'. essentially of suchblended silicone-diesterr basefluids as described above having dispersedtherein between about 5 to about 30 per cent by weight ofy metal soapthickener.

the ease of preparation andthe-properties olo-l tainable from the'blending of the above-de- 7 scribed components in varying parts byWeight.

EXAMPLE I A base uid lubricant was prepared by mixing together 60.8partsy of poylmethylphanylsiloxane (aromatic-aliphatic ratio-.51) havinga viscosityfof about 50 cntistokesv at 25. C., 25 parts butyl2fpheny1phenol and heating with stirring to about 400 F. Thirteen (13) partsoflithium stearate was -added to this hot base fluid and the mixture wasstirred until ,a clear solution resuited. This solution ,was then/cooledrapidly to form a gel, which gel was worked about ten times through a[70 x 80 mesh screen to produce a grease of uniform consistency.

The grease had an ASTM penetration at '77 F.

of 224. Afterbeing forced through a 400 mesh screen'100 times, thepenetration had increased to only237. After`500 hours at 210 F.-in,theNorma-Hoffman Oxidation Test, a drop frompounds per square inch to 108.5pounds per squareinch in oxygen pressure'indicatesv the high degree ofoxidation resistance of this grease.

.After 50 hours at 212 F. the grease which .had

been forced through the 400 mesh screen 100 The following examples willserve to illustrate "grease preparedas described in Example@ It ytorque' properti lithium stearate were bleeding offonl'y- 6.3 'pretions.

Ak base fluid lubdicant 'was prepared .by

ing 65 'parts of polymethylphenylslloxane 4faro matic-aliphaticratio-7.51) having a viscositygt 'about 50 centistokes at 25 C., and 25.par ts oi.

` di-Zfethylhexyladipate asfin Example I. Ten' (I Olparts' of lithiumstearatewas addedand a..

*that of Example I in the omissione! balancing"` ingredients. T hisexample isgiven` to emphasize the fact that balancing ingredientsmay beused' asin Example I I to imp'rove vspecfic properties y of a greasewithout detrimentally eiecting its 2"l primary chemical and lubricatingqualities.

rThis grease had en asm penetration et 17 F.; of 240and after 50 hoursat 212' Fnthe grease'. which had been forced through'a 400 mesn'screenI100 times showed'bleedin'g.oionlyl 3.6 per cent andevaporation of/only0.54 per cent.: l. Exmrrli Twenty-three 23) parte of -poiymetnviphenyufsiloxane (aromatic-aliphatic ratio-51) having 3 a viscosity of about5'o oenustokesjet .25\o., ce

parts of ,di-2-ethylhex`yl sebacate. and ll parts of lithiumstearatewere used to prepare ai grease .i a

asin Example I.

This grease had an ASTM penetr of 231 and after 50 hoursat 212 F. showedbleed..

ing of on1y`-4Ld `per cent 'and evaporation of only- 0.47 percent;Balancing ingredients to enhance specific lubricating or load' carryingqualities of the grease may be incorporated in this composh,

tion, as in any other grease of the type involved in this invention,without materially changing lthese fundamental` qualities. This' greaseis a' highly eiective lubricant over a temperature range from 'about 50F. toabout 300 F. and is characterized 'by its extremely low starting- AVExlumjLnIV 'Sixty-two v(62) parts of polyniethylsiloxane 5 having aviscosity of about 5 centistokes at 25C., 25. parts of di-2- ethylhexyls'ebacate, and 13 parts o f lithium stearate were used to prepare agrease as in Example,I. This grease gave an ASTM penetrationat 77 F.; of254, and after being -5 fforcedthrough a 250 mesh screen 100 times, the

' penetration was only 263, 'lifterv 50 hoursv at 212 the grease showedbleeding of only 2.3V per cent andi evaporation 'of only 0.52 per cent.

'torque-properties. It is an eiective lubricant over a temperature rangefrom about 125 F. to about'200 F.' .o

'Forty-ve ('45) parts of `polymethylphenyl- 'siloxane(aromatic-aliphatic .ratio-.51) having a viscosity of about 50centistokes at 25. C.. 45 parts of. di-tetradecylsebacate, and 10 partsof used to prepare a grease? as in E xampleI.

This grease gave anl ASTM penetartion at 77 F. of 239, and after50hoursat 212 F. showed o ent and evaporation of only 0.70 per centr. r

1-gamin) 00 F. in high-speed lubricatingapplica-,-

the preceding example'sior 'purpos V :qualities'oi various lithium soapcreases.v The A examples to follow are 'to illustrate that the. prac-'.isti'caare utilized-'roil specific lubricating funclo: n.ji.lu'stration-,I have'described thepreparation and 5f tice of myinvention is just as readily applicable -eto the'preparation oi'othermetal-soap Ereases .f ,.'whiclL Lb/ecause of 'their individualcharacter .tio'ns.- The general properties and'a'pplications` 10.tojwhich each type of metal soap kgrease is preiwm be noted that this,oo'mposmonemers freni- 15' mem mi used' ation at '77' F. `35

erentially adapted is well known in theflubricatl art and forlnsnopartof the presentinven- .'tion. It'iS to y.

noted that the characteristics which are dire srease-,contributed'bythebase fluid are "Idennitely'mprover f siloxane. (aromatic-faliphaticratio-.51) lhaving -a viscosity .oiabout 50 centistokes at 25 C., 25

or di2ethy1hexy1sebeoete,end 1s parte ofv 25 aluminum stearate were usedfto prepare a grease y phenylsiloxane -(aromaticaliphaticratio-3.51)v i havingV a viscosity of about 100 centistokes at 25 C. 20parts of ydi-2-ethylhexyl azelate; and 14 parts of strontium palmita'te.The. penetration measured at.77 F, was 235.

For purposes cf il1ustrat in general terms'in Example I/a method wherebythe. 'grease-compositions of my invention may be '0 produced. That is tosay, the various ingredients may be heated together, with stirring untila clear solution `is obtained, which solution is suddenly lchilled toambient temperature to produce a composition have a grease structure.This meth- 45 od has proved successful'in all cases. However,

in .order to produce a grease composition having essentially a. siliconeuid as its base, thatds, 'a'

silicone grease, I ha method. The thickening soapis iirst dispersedinthe e discovered the following silicone iiuid where it is maintained insuspension by. a suitable stirring or mixing means. The suspension isheated'to a {solvation temperature of the soap, which temperature isdetermined em- 5 pirically andis dependent upon the type andquantity ofingredients beingproces'sed. lAt this 'solvatin temperature,` which in'generaiwill be .within the range of 250 F. to 400 F., a diester fluid isadded to the system in an' amount just` This grease 1 5 especiallyadapted@ Se in den 60 suiilcient to dissolve the soap and produce aclear cate instruments by virture of its low startinghot solution. Uponsudden chilling of the'hot solution to ambient temperature, a grease isproduced which is essentially 'a silicone base grease.

It should be notedthat my 'invention isnot 5 limited to the use ofliquid silicones in the prep-- .'aration 'of the base fluid lubricants.I have usedr ester-soluble solid polymers of silicones, such aspolymethylphenylsiloxane resins, in preparing `excellentgreases havingproperties similar -to 0 those illustrated in the above examples.

contributed by` thel type of the" preparationoi greases -arenotechanged; but that the properties of the Fifty-seven (52) parts "ofpolymethylphenyl,

pared as in Example I: 66 parts-of polymethyl ion, I have "described byweight v'oi'. lithium stearate'r-The method oi Icompounding the greaseis the-sameas that here-- 5- to 'about so parts by inbefore described.The ASTM penetration of '77 F., after forcing the grease through' '10 x80- mesh screen eleven times was 233."- This grease is well adapted tofine instrument operation be- Ycause of its low: starting-torqueproperties.

' According* to my y invention', many superior greases can be preparedfrom mixtures of diesters and silicones thickened with various metalsoaps.

' These greases have remarkable oxidation stability, low 'bleeding andevaporation rates,'high s l weight of a metallic soap of a saturatedaliphatic' acid and'from about 95 to about 70 parts A by weight offabase fluid component, said acid having from at least to about carbonatoms in the aliphatic chain, said base fluid comprising a mixture offrom-about 5 to about 95 parts by weight of adiester of a dicarboxynoao1d,and.from about 9 5 to about 5 parts by,weight of a silicone, andsaid-base uid compopart4 by weight ofv 4-tertiary butyl-2-phenyl shearstability,'and are water-resistant and heat stable. I-Iigh temperaturegreases operating at temperatures up to 300 F, and low temperaturevgreases operating as low as -100 F. can be pre- .pared by varying thetype of'Y silicone and thedii ester used. They can be prepared morecheaply and more easilylthan greases made from a silicone fluid alonewithout sacrificing any' of the desirable silicone-imparted operatingcharateristics. l Since many vmodifications may be made in my inventionwithoutdeparting from the -scope thereof,'it is to .beunderstood thatthis invention is not restricted to 'the present-disclosure otherwisethan defined by the appended claims.

Theinvention described herein Amay be manunent having dissolved thereinless than about 1 6. A grease composition comprising, 5 parts by weightof lithium stearate, 27 parts by weight of afdimethyl silicone, 65 partsby weight of ldi2 ethyl hexyl adipate, 2 parts by Weight of 4-ter' tiarybutyl-Z-phenyl phenol, Aand I1 -part by weight of polymethylmeth'acrylate.

.7. A grease compositionI comprising, 27 parts by weight of lithiumstearate, 23A parts' by weight f ofA a polyphenyl-methyl silicone, .50par-ts by weight of di-Z-ethylhexyl' sebacate.

factured and used by or for the Government of the United States ofAmerica for governmental purposesI without the payment of any royaltiesthereon or therefor.

What is claimed is`:

8..A grease composition comprising, 13 parts by weight of lithiumstearate, 62 parts by .velght of a dimethyl silicone, and 25fp'afts bywe*y ght di- 2-ethylh'exyl azelate. 9. The method of producing asilicone grease which comprises, rmaintaining la dispersion of metalsoap particles in a siliconev iiuid, heating said dispersion toy aboutthe solvation temperature of saidsoap, adding a diester of adicarboxylic acid to said dispersion at said solvation ,temperature inan amount sulcient to cause said \1 A grease composition compatible withthe l raddition of relatively small .proportions of polymer thickeners,oxidation, rust and corrosion inhibitors and extreme pressure additivescomprislng, 5 to 30 partsby weight of a metallic soap and 95 to 70 partsof a 'uid blend`of between about 5 and about l95 parts by weight of adiester of a dicarboxylic/'acid and between about 95 and 5 parts byweight of a silicone.

'2. A grease composition comprising 5 to 3 0 parts .,b'y weight of ametallic soap and 95 to 70 parts by Weight ota fluid blend of betweenabout 5 and about 95 parts by weightofa diester of a dicarboxylic acidand between about 95 and about 5 parts by weight of a dimethyl silicone,said base iiuid component having'fdissolved therein less than 3 parts byweight of a mixture of a polymer thlckener, oxidation, rust andcorrosion inhibtors and extreme pressure additives.

3. A grease composition comprising, 5 to 30 parts by weight of ametalli-c soap of a .fatty acid dispersed in a, basekfluid as athickener therefor,

soap to go intosolutionand chilling said solution rapidly to ambienttemperature.

' 10. The method of producing al silicone grease which comprises,maintaining a dispersion of a 'metal soap in av phenyl-methyl silicone,heating said disperison to the solvation temperature ofpolymethylphenyl-siloxane with from about 5 to said base fluidcomprising a blend of 5 to 95 parts l by weight of a diester ofdicarboxylic acid and 95 to 5 parts by Weight of a slicone, andV saidbase uid having dissolved therein approximately 3 parts by weight of amixture of oxidation andv rust inhibitors and extreme pressure. andanti-wear. additives.

4. A grease composition compatible withjhe addition of relatively smallproportions of polymer thickeners, oxidation, rust and corrosioninhibitors and extreme pressure additives, comprising 5 to 30 parts byweight of a lithium soap of a saturated fatty acid andf95 to,70 parts byweight of a base fluid component, said acid having from at least 10 toabout 20 carbon atoms in thealiphatic chain and said base uid componentcomprising a blend of 5 to 95'parts by weight of adi- 1 ester of adicarboxylicacid-and 95 to 5 parts by weight of phenylmethyl silicone.

. G5. -A grease composition comprising, fromabout about 95 parts byweightof a di-ester of a dicarboxylic acid,' heating the solution soformed l`to a temperature of about 400 adding from 5 to 30 parts of ametallic soap of a fatty acid to from 95 to '70 parts by weight'of thesolution, stir- .ring the resulting solution of the soap until clear andrapidly cooling the said resulting solution to form a gel and'grease ofuniform consistency.

1Roaring' L. MERKER.

REFERENCES CITEDl The following references are Aof record' in the iileof this patent;

UNITED STATES PA'IIEiNTs Name 4 Number Date l `1,993,738 Graves et al.Mar.. 12, 1935 2,049,072 Mikeska et al. July 28, 1937 2,104,408Wiezevich Jan. 4, 1938- 2,406,911 sowa sepa-3, 1946 2,407,037 -Sow'a L eSept. 3, 1946 2,410,346 f Hyde oct. 2 9, 194e

